Question

A tire company measures the tread on newly-produced tires and finds that they are normally distributed with a mean depth of 0.84mm and a standard deviation of 0.35mm. Find the probability that a randomly selected tire will have a depth less than 0.24mm. Would this outcome warrant a refund (meaning that it would be unusual)?

Answer 1

4.32%; no

Explanation:

The value of 0.24 differs from the mean by 0.84 -0.24 = 0.60. 2 standard deviations from the mean would be a difference of 2×0.35 = 0.70.

A statistical calculator says the probability of a depth less than 0.24 mm for the given distribution is about 4.32%.

The value differs from the mean by less than 2 standard deviations, so is not considered unusual.